The molecular genetics of nervous system tumors

Familial glioblastoma

The authors describe a family with three members affected by glioblastoma. The proband patient, a 7 year-old girl, developed a rare complication, a pulmonary metastasis. Chromosomal analysis of her peripheral blood lymphocytes showed a normal karyotype (46, XX), without structural abnormalities. Cytogenetic study of the tumor cells disclosed several abnormalities: 46, XX, 7q-/46, XX, -2, 4p-, 7p-, +15/46, XX. Some aspects about genetics of glial neoplasms are discussed.

Analysis of c-erbB2 protein content of human glioma cells and tumor tissue

This study was designed to determine whether or not overexpression of the c-erbB2 protein plays a role in the etiology of human gliomas. The c-erbB2 gene codes for a 185 kDa cell membrane glycoprotein (gp185c-erbB2), which is similar to the receptor for epidermal growth factor. In initial studies, four human glioma cell lines (A-172, U118MG, U138MG and SW608) were used to develop techniques for detecting and quantifying gp185c-erbB2, using immunofluorescence microscopy, immunoblot analysis and flow cytometry. A-172 cells were found to have the highest content of gp185c-erbB2. More detailed studies utilizing A-172 cells indicated that cellular gp185c-erbB2 content changed little in response to conditions affecting cellular proliferative status, including serum deprivation, growth in low glucose medium and treatment with dimethyl sulfoxide. Ten human glioma specimens were then analyzed for cellular gp185c-erbB2 fluorescence and DNA content, using A-172 cells as a biological standard. Results indicated that gp185c-erbB2 was expressed at levels comparable to that of A-172 cells in many specimens, and at a very high level in one specimen. These data reiterate the problem of the molecular heterogeneity of human gliomas and indicate that gp185c-erbB2 may have a role in at least a subset of malignant glial tumors.

Expression of neu/c-erbB-2 in human brain tumors

The neu/c-erbB-2 oncogene encodes a 185 kd transmembrane protein (p185). Here we have used the monoclonal antibody (mAb) 3B5 to determine the expression of p185 in a series of fixed biopsy specimens of 180 human brain tumors, including the most frequent entities and, in addition, 18 recurrent gliomas with malignant progression. In summary, 3B5 immunoreaction was most prominent in astrocytomas of different grades of malignancies and in meningiomas. In World Health Organization (WHO) grade II astrocytomas mab 3B5-immunoreaction was related to the cytomorphological phenotype. Fibrillary astrocytomas showed no or only a weak immunoreaction (four of five, 80%) in contrast with protoplasmic or gemistocytic astrocytomas, where a strong reaction was observed in most cases (six of nine, 66.6%, and four of five, 80%, respectively). In WHO grade II to WHO grade IV astrocytomas a trend towards higher scores with increasing grade was found. In a limited number of cases (18 gliomas and two meningiomas) of the tumor series tested other mAbs against neu/c-erbB-2 epitopes, especially the mabs 9G6 and CB11, gave qualitatively comparable results. In WHO grade I pilocytic astrocytomas a wide range of 3B5 immunoreactivity has been observed. The results of in situ hybridization using a 32P-labeled neu/erbB-2 RNA probe performed on four WHO grade I and II astrocytomas, seven WHO grade IV glioblastomas, one WHO grade II oligoastrocytoma, one WHO grade III anaplastic astrocytoma, and three WHO grade I meningiomas were consistent with these immunomorphological data, and Northern blot analysis also indicated an overexpression of neu/c-erbB-2 mRNA in gliomas of different grades of malignancy and in meningiomas. These elevated neu-erbB-2 transcript levels occurred in the absence of gene amplification. In a second series of recurrent gliomas with malignant progression (n = 18) the higher 3B5-immunoreaction scores were apparent in the more malignant recurrent gliomas. In this series the overexpression of neu/c-erbB-2 parallels glioma progression. In our cases it was not, however, correlated with the postoperative relapse-free interval or with the overall length of survival.

Specific inhibition of c-sis protein synthesis and cell proliferation with antisense oligodeoxynucleotides in human glioma cells

The protein encoded by c-sis is overexpressed in human neuroglial tumors and has been hypothesized to play an important role in tumorigenesis. To address this issue, we examined the effect of an 18-base pair oligodeoxynucleotide complementary to a sequence starting of ATG initiation codon of mRNA of c-sis upon glioma cell growth. First, we investigated the expression of c-sis within cultured human glioma cell lines and also fresh glioma specimens by using polymerase chain reaction. We could detect messenger ribonucleic acid transcripts of c-sis in three of four glioma cell lines and two of five glioblastoma multiforme specimens. This finding was confirmed by dot-blot hybridization with a specific oligonucleotide probe of c-sis. The antisense oligonucleotides complementary to c-sis messenger ribonucleic acid were efficiently incorporated into A172 cells in vitro, and kinetic studies showed that maximum uptake was seen after 48 hours incubation with antisense oligomers. Exposure of human glioma cell lines to antisense oligodeoxynucleotides targeted against the first initiation codon of c-sis inhibited cell proliferation in a time- and dose-dependent fashion. From flow cytometric analysis with anti-c-sis sera, it was demonstrated that the antisense oligomers specifically block the de novo synthesis of intracellular c-sis protein by glioma cells. In contrast, the corresponding sense oligomers did not inhibit either synthesis of c-sis protein or glioma cell growth. These results clearly support a role of c-sis protein in the proliferation of these human neuroglial tumors and show that inducible protein expression can be blocked by means of synthetic oligonucleotides complementary to a coding exon.

Oncogenes: cause or consequence in the development of glial tumors

Recent developments in the field of oncogenes and growth stimulatory factors have provided limited but essential models in neuro-oncology. The observation in gliomas of platelet growth factor (PDGF)-like immunoreactivity fits with the autocrine secretion model, rising the possibility for the growth factor independence of the cancer cells. The discovery of the tumor suppressor genes, for which loss of function mutations are oncogenic as in the RB gene of the retinoblastoma and p53 gene, has introduced a new concept of oncogenesis which could be useful even in the cure of the neoplasms. Several oncogenes are amplified and/or expressed in brain tumors, some associated with polymorphism leading to abnormal protein products. Therefore, corresponding functions, such as production of deficient epidermal growth factor receptor (EGFR) encoded by erb-B, are impaired. Abnormal chromosomal patterns have been recognized in brain tumors and found mainly in chromosomes 7 and 22 on which oncogenes erb-B and sis are located, respectively. Location of proto-oncogenes, which are normally expressed in the brain, indicate that they share common distribution patterns mainly involving the cerebellum, hippocampus and olfactory bulbs. These proto-oncogenes may be regulated by physiological and pathological events. The concept of oncogene involvement in brain tumors must be extended to include the other factors such as G-proteins, growth factor receptors, membrane-associated and cytoplasmic protein kinases, which are all responsible for the control of the cell growth and their response to external signals including chemotherapeutic drigs.

Loss of constitutional heterozygosity in chromosome 10 in human glioblastoma

Gene deletion of chromosome 10 in 11 tumor tissues removed from nine patients with malignant glioma (seven glioblastomas and two malignant astrocytomas) was investigated. Loss of heterozygosity was found in four of the seven (57%) cases with glioblastoma, whereas heterozygosity was preserved in two malignant astrocytome cases. One glioblastoma case showed loss of heterozygosity only in the recurring tumor tissue, although heterozygosity was maintained in the initial tumor tissue. The significance of loss of heterozygosity in the growth and recurrence of glioblastoma is discussed.

Enhanced expression of the sis and c-myc oncogenes in human meningiomas

In 19 human meningiomas (14 primary and four recurrent tumors and one tumor transplanted into athymic nude mice), oncogene expression, amplification, and rearrangement, and loss of heterozygosity on chromosome 22 were examined. Compared to nontumor brain tissue, there was greater than a fivefold expression of the sis oncogene in six (40%) of 15 tumors studied and of the c-myc oncogene in 12 (63%) of the total 19 tumors. Expression of the sis gene was lower in the recurrent tumors than in the primary cases, and there was no detectable expression in anaplastic meningioma cells. Rearrangement of the sis gene was found in one meningioma. Loss of heterozygosity on chromosome 22 was detected in two of the five informative heterozygous cases. Expression of the c-myc gene was higher in cases with a loss of heterozygosity than in those without. These results suggest that the sis and c-myc oncogenes are associated with tumorigenicity and that c-myc may induce meningiomas through loss of the putative tumor suppressor gene.

Trends in neurosurgery. The 1989 AANS presidential address

This overview of neurosurgical practice examines patterns of case management, using several areas such as head injury, brain tumors, and the delivery of health care to illustrate the changes that have taken place over the past 40 years and the changes that might be expected in the next 40 years. The rapid pace of progress has indicated further exciting growth of this specialty into the 21st century; however, what remains constant is the dynamic character of the neurosurgeon. This view of the past and the possibilities for future innovation enables neurosurgeons of all generations to have a sense of pride in the achievements generated by their peers.

An update on the cellular and molecular biology of brain tumors

Patients with tumors of the central nervous system (CNS) remain difficult to treat despite recent advances in surgical, chemotherapeutic and radiotherapeutic techniques. A better understanding of the molecular and cellular biology of neoplasia is providing neuroscientists with a framework on which to devise novel therapies for these patients. It thus becomes imperative that neurologists and neurosurgeons be aware of these advances in basic science that may eventually have a positive impact on patient management. This paper reviews our present knowledge of the process of CNS oncogenesis and the roles that chemicals, viruses, oncogenes, growth inhibitor genes, and growth factors play in the process.

Oncogenes and neuro-oncology

The application of molecular biological techniques to the study of lympho-erythroid neoplasms, colo-rectal carcinoma and neuroblastoma has led to fundamental insights into the nature of cellular proliferation, transformation and immortalisation as well as providing prognostic information about the biological behaviour of certain tumours. The study of the molecular genetics of central nervous system tumours with particular reference to oncogenes is however in its infancy. Most of the current literature concerns studies of small numbers of glial tumours or of glial tumour cell lines. In this review the results of these studies are analysed and compared with relevant oncogene findings in experimental cerebral neoplasia, extracranial tumours and postulated mechanisms of oncogene activation. The role of proto-oncogenes in the development of the brain, and the clinical relevance of advances in molecular biology to central nervous system neoplasia are discussed.